Problem: Tiffany ate 4 slices of pizza. Vanessa ate 3 slices. If Tiffany ate $\dfrac{4}{12}$ of the pizza, what fraction of the pizza is remaining?
If 4 slices represent $\dfrac{4}{12}$ of the pizza, there must have been a total of 12 slices. $\text{fraction of pizza remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 7 slices, which leaves 5 out of 12 slices remaining. There is $\dfrac{5}{12}$ of the pizza remaining.